EXPLANTING AND CULTIVATING 



435 





Summary diagrams based on a study of over 50 blasto- 

 derms growing in ovo and stained as shown in (a) with 

 a 1:1 mixture of 0.596 Nile blue sulfate and 0.5% 

 Neutral red. In (b) is shown the position of the stained 

 band of cells 6 hours later. In (c) (drawn to a some- 

 what smaller scale than a and b) is shown the pattern 

 of stained cells 14 hours later (20 hours after the original 

 marking as in a). If (c) be compared with (b) it is to be 

 noted that the end-bud and the neural tube have second- 

 arily acquired the stain and keep it in the oxidized (blue) 

 state. In the region just anterior and lateral to the bases 

 of the omphalomesenteric arteries no stain can be seen 

 (presumably it is in the reduced (colorless) state). The 

 stained regions lateral and parallel to the neural tube 

 are in the lateral plate mesoderm (cf. Pasteels, 1937, 

 fig. 18). No exceptions to this result have been found. 



Diagrams illustrating the pronounced anteroposterior 

 "stretching" of the pre-nodal region (neural plate), 

 the absence of invagination through the primitive 

 pit, and the presence of invagination just behind 

 the node during the early stages of regression of the 

 streak. Time increases from left to right in the 

 diagrams. Note the more rapid and extensive re- 

 gression of the primitive streak relative to marked 

 areas lying lateral to it. 



Two above diagrams from Spratt 1947: 

 Jour. Exp. Zool. 104:69 



A-LIVER 

 ^-MEART 

 ©-CHORDA 

 a-THTROID 

 ©-NEPHROS 

 X -INTESTINE 

 ■ -EBYTHROCrTE 

 X-MELANOPHORES 

 + -SKELCTAL MUSCLE 



DISTRIBUTION OF POTENCIES IN THE DEFINITIVE 



PRIMITIVE STREAK BLASTODERM, TESTED UNDER 



VARIOUS EXPERIMENTAL CONDITIONS 



Ectodermal potencies shown on left, mesodermal and 

 entodermal on right; these have not been tested sepa- 

 rately. Posterior and lateral extent of mesodermal 

 potencies has not been specified. 



From Rudnick 1944: Quart. Rev. Biol. 19:187 



